1. Field of the Invention
This invention relates to an intersection emergency warning system and more particularly to an intersection emergency warning device which is separate from and operated independently of other intersection traffic control devices.
2. Description of the Prior Art
When emergency vehicles such as police cars, fire engines, ambulances, etc. are summoned to the scene of an emergency, these vehicles are authorized by law to safely pass through intersections in disregard of the automatic intersection traffic control devices. The emergency vehicles utilize visual and audible warning devices mounted thereon to alert nearby persons of their approach. However, due to man-made or natural obstructions near the intersection, the high ambient noise level within modern cities, and the inattention of those in the proximity of certain intersections, the emergency vehicles are often involved in vehicular accidents when other motorists negligently disregard the warning signals.
Several intersection warning systems have been devised which utilize a radio receiver to receive a signal transmitted from an emergency vehicle approaching the intersection. These warning systems often provide the capability whereby the operator of the emergency vehicle may control the intersection traffic control device--generally a traffic light--so that three of the approaching directions receive a red light at the intersection, while the roadway in the direction of travel of the emergency vehicle receives a green signal to clear stopped traffic therefrom. In the alternative, all four directions may receive red lights. The operation of the normal intersection traffic control device is captured by the presence of the emergency vehicle as previously explained and then released into normal operation upon the departure of the emergency vehicle from the proximity of the intersection. Such a system for emergency vehicle control of traffic signals is disclosed by Coll et al in U.S. Pat. No. 3,638,179. While this type of system is effective for the emergency control of traffic at congested intersections, the great complexity and concomitant expense of these systems prohibit their use in all but the most heavily traveled and dangerous intersections. A similar emergency traffic control system is disclosed by Koch in U.S. Pat. No. 2,203,871.
One variation of the radio controlled intersection emergency warning system is disclosed by Long in U.S. Pat. No. 3,550,078, in which an optical or infrared energy source is utilized by the emergency vehicle to actuate the intersection traffic control systems. Another variation is disclosed by Harsanyl in U.S. Pat. No. 3,636,507 in which a second light bulb is placed within the individual reflector assemblies of each of the lights of an intersection traffic control device. The additional light bulb is energized through a radio operated switch by an approaching emergency vehicle. The switch also interrupts the power to the normal red, green and yellow lamps.
Schwab in U.S. Pat. No. 2,963,674, discloses a remote emergency traffic control system which uses a radio transmitter means carried by an emergency vehicle for activating all of the red signal lights of the normal intersection traffic control device upon the approach of the intersection by the emergency vehicle. An auxiliary light is positioned near the intersection and is activated responsive to the signal transmitted by the emergency vehicle, thereby informing the emergency vehicle that it has control over the intersection traffic control device. When two emergency vehicles attempt to control the same traffic signal, a special circuit causes the auxiliary light to flash alternately on and off. In this manner multiple emergency vehicles attempting to cross the same intersection will be forewarned of the presence of other similarly intentioned emergency vehicles. A similar system for emergency remote control of traffic signals is disclosed by Mentzer et al in U.S. Pat. No. 3,209,325. However, the Mentzer system places the control verification light within the emergency vehicle rather than adjacent to the traffic intersection. An alternate alarm is also included to warn one emergency vehicle of an attempt by the second emergency vehicle to access and control the intersection traffic control device.
While these systems for allowing the control of intersection traffic control devices by approaching emergency vehicles are generally cost effective in densely populated cities having substantial emergency vehicle traffic, the complexity and the expense of this type of system prohibits their use in more sparsely populated areas such as the suburbs of the large cities or smaller towns. The present intersection emergency warning apparatus has been designed to fill this need. The intersection emergency warning apparatus is relatively inexpensive to produce and can be installed adjacent to normal intersection traffic control devices and operated completely independent thereof. No alterations or modifications are required to existing traffic control devices at the intersection, which further minimizes the cost of installation and operation. In addition to the normal visual warning devices utilized by the prior art inventors, the present invention utilizes an audible warning means to attract the attention of those who are inattentive to the visual intersection traffic control device.